3. Diagnosis of the SI joint as the primary lower back pain generator based on ALL of the following: a. Patient has pain at or close to the posterior superior iliac spine (PSIS) with possible radiation into buttocks, posterior thigh or groin and can point with a single finger to the location of pain (Fortin Finger Test), and b. Patient has at least 3 of 5 physical examination maneuvers specific for SI joint pain, and c. Patient has improvement in lower back pain NRS of at least 50% of the pre injection NRS score after fluoroscopic controlled injection of local anesthetic into affected SI joint(s) (including previous documented test <6 months ago)